Pinnacles National Monument Air Quality Information
Overview
Pinnacles NM is located within California ’s North Central Coast Air Basin on the border of San Benito and Monterey counties. The area has experienced rapid growth in recent years, with development of the cities of Monterey, Hollister, Salinas, and the smaller cities of the Salinas Valley. The 2000 census of San Benito County showed a growth rate of 71 percent over the preceding 10 years. The principal air pollutants of concern in the monument are ozone precursors (nitrogen oxides and volatile organic compounds) from mobile sources and particulates from road dust, agricultural activities, and burning. Sulfur dioxide emissions are relatively low in the area.
The air quality related values (AQRVs) of Pinnacles NM are those resources that are potentially sensitive to air pollution and include visibility and night sky, water quality, soils, vegetation, and wildlife. In addition, Pinnacles NM has two registered integral vistas that are protected under the Clean Air Act.
Visibility is a very sensitive AQRV in Pinnacles NM. Although visibility in the monument is still superior to that in many parts of the country, visibility in the monument is sometimes impaired by light-scattering pollutants (haze). The U.S. Environmental Protection Agency’s Regional Haze regulations require States to establish goals for each Class I air quality area to improve visibility on the haziest days and ensure no degradation occurs on the clearest days. As part of the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, visibility in Pinnacles NM has been monitored using an aerosol sampler (1998-present), a transmissometer (1988-1993) and an automatic 35mm camera (1986-1995). An analysis of 1990-1999 data from the monument indicates that visibility in the area is improving on both the clearest days and the haziest days.
Surface waters in Pinnacles NM are well buffered and unlikely to be sensitive to acidification from deposition of nitrogen and sulfur compounds. However, soils and vegetation in the park may be sensitive to nutrient enrichment from nitrogen deposition. There is evidence that atmospheric deposition of nitrogen may play an important role in the ongoing replacement of native plant species with exotic, invasive annuals in coastal sage scrub vegetation communities of California. Native plants that have evolved under nitrogen-poor conditions are replaced by invasive species that are able to take advantage of increased nitrogen levels. This phenomenon has not been documented in Pinnacles NM. However, nitrogen deposition rates, although relatively low in the monument, are elevated above natural deposition rates and may be causing subtle changes in vegetation communities.
Estimates of total atmospheric deposition can be made by adding wet and dry deposition. Wet deposition has been monitored in Pinnacles NM from 1999-present as part of the National Atmospheric Deposition Program/National Trends Network (NADP/NTN). The site ID is CA66. Dry deposition has been estimated for Pinnacles NM (site PIN414) since 1995 as part of the Clean Air Status and Trends Networks (CASTNet).
Several plant species that occur in Pinnacles NM, including Sambucus mexicana (blue elderberry) and Artemisia douglasiana (Douglas’ sagewort, mugwort), are known to be sensitive to ozone. Ozone has been monitored with a continuous analyzer from 1987- present in the monument. In recent years, ozone concentrations have exceeded the 8-hr ambient air quality ozone standard of 85 parts per billion on a number of occasions. In addition to these high peak concentrations, ozone cumulative doses are sufficient to induce vegetation injury.
In addition, Pinnacles NM historically has had a great abundance and variety of lichens, which give the namesake pinnacle rocks their varied hues. Many of the species present are known to be sensitive to air pollution and may be impacted already.
Additional information relative to air quality and air quality related values at Pinnacles NM is available in T. Sullivan et al. 2001. Assessment of Air Quality and Air Pollutant Impacts in Class I National Parks of California (April 2001, pdf 6.24mb). National Park Service. Denver, CO.